High levels of organic detergent surfactant (active) are sometimes required in laundry detergent compositions, particularly in compositions intended for washing by hand, to give effective soil removal. However, it has been found that problems of poor powder properties can be encountered in high-active compositions, for example, powder stickiness leading to agglomeration and poor flow.
Flow properties are improved by the presence of inorganic materials having a good carrying capacity for mobile organic surfactants, but the higher the intended surfactant level, the less room there is in the formulation for inorganic material.
Clearly it is preferable that the inorganic material included for this purpose should also itself have functionality, for example, as a detergency builder. However, one of the most effective and popular detergency builders, sodium tripolyphosphate, has a relatively poor carrying capacity for surfactants unless spray-dried.
In order to improve the liquid carrying capacity of particulate detergent compositions to allow a high active level, it is known in the art to include a relatively high proportion of material, typically builder material, which has a better carrying capacity than sodium tripolyphosphate. For example, zeolite may be used in this role. However, zeolite is insoluble and its presence may lead to residues on washed fabrics. The present inventors have therefore sought to provide particulate detergent compositions having a high surfactant content, yet having acceptable or good powder properties, without the need to incorporate substantial quantities of zeolite.
Traditionally detergent powders contain a base powder, prepared by spray-drying or granulation or a combination of such processes, consisting of structured particles containing all, or the major part of, the surfactant and builder in the formulation. Other ingredients not suitable for incorporation in the base powder, such as bleaches, enzymes, heat-sensitive nonionic surfactants, antiredeposition polymers, dye transfer inhibiting polymers, foam control granules, and perfumes are subsequently sprayed on to, or dry mixed with, the base powder.
The present inventors have discovered that free-flowing powders having higher surfactant to builder ratios than have previously been possible may be prepared, if the base powder is partly or wholly replaced by, or supplemented with, separate granular components in which certain ingredients are concentrated, or segregated from one another.